This Small Business Innovation Research Phase 1 project will develop a hard-x-ray microscope capable of producing dark-field images for the detection of colloidal gold particles. Gold colloidal particles are used as labels in the study of antigens and cell and protein structure. In prior research, Adelphi Technology Inc. has developed compound refractive lenses for use in an x-ray microscope that has been used to image biological material in the bright-field mode. A prototype dark-field microscope will be developed by modifying this existing microscope. The potential for successful development of the prototype imaging system is very high because prior work by other researchers using synchrotron sources that have demonstrated the ability to detect gold particle sizes down to 20 nm in very thin specimens. The use of harder x-rays promises detection of smaller size particles inside thicker specimens and the possibility of the use of tomography for volume analysis. Replacing the synchrotron with a conventional x-ray tube as the x-ray source permits commercial and scientific use outside national laboratories. Issues to be explored in Phase I include: adequacy of x-ray source intensity, dose to specimen, expected contrast, and resolution.